Wireless communication can be realized either in a circuit switched (CS) architecture, or in a packet switched (PS) architecture. Circuit switched networks utilize a continuous connection for user data exchanges. For example, a circuit switched cellular network connects one mobile device through the cellular network to another mobile device using a “fixed” connection. CS routed connections remain unchanged for the duration of the connection. In contrast, Packet switched networks do not have a “fixed” connection like CS connections. Instead, PS connections are routed flexibly on a network of elements; the underlying transport route is not pre-defined and may dynamically hop between network elements.
PS networks segment data into small “packets” for transfer. Each packet comprises a mutable Network Address (e.g. Internet Protocol (IP) address) of both the source and destination terminals. On a low level, PS based calls are fluid; however, high level software negotiates various parameters to ensure integrity of the connection (i.e., that all packets will be received), using redundancy, or error correction, etc., and also imposing any QoS requirements (e.g., latency). PS connections may be configured to support such varying application requirements, such as data latency, throughput, bandwidth, robustness, etc.
The differences in operation between circuit-switched and packet-switched delivery models are sometimes incompatible. However, for various reasons, interoperation between circuit switched and packet switched networks is desirable. For example, within cellular networks, early incarnations have been primarily circuit switched. However, with newer data technologies, cellular networks are migrating to packet switched network topologies. Moreover, even circuit-switched cellular networks may bridge to packet-switched networks via, e.g., gateways and other similar components.
GSM, GPRS, EDGE Network Interoperation—
GSM (Global System for Mobile communications) is one exemplary implementation of a “second-generation” or “2G” cellular telephone technology. GSM technologies are circuit switched. GPRS (General Packet Radio Service) is a packet-oriented mobile data service available to users of GSM to support packetized data services. GPRS is considered a 2.5G cellular technology, and uses the same Radio Access Network (RAN) as GSM. EDGE (Enhanced Data rates for GSM Evolution), or Enhanced GPRS (EGPRS), provides still further improvements to existing GSM networks. EDGE is considered a “third-generation” or “3G” cellular technology and is a fully packet switched network.
The GSM, GPRS, and EDGE mixed networks bridge the gap between circuit switched and packet switched networks. Unlike fully CS based networks or fully PS based networks, mixed networks (i.e., that support CS and PS based routing) are subject to special considerations and constraints. For example, the Dual Transfer Mode (DTM) protocol enables CS voice and PS data coexistence on the same GSM radio channel. A mobile phone which is DTM-capable can support simultaneous voice connections (via CS), and packet data connection (via PS) in GSM/EDGE networks. The implementation of DTM capability is not straightforward, and GSM/GPRS/EDGE equipment is further subdivided into various classes offering various degrees of legacy support. Mobile devices are split into Class A, Class B, and Class C devices. Network devices may operate in three (3) Network Operation Modes (NMOs): NMO-1, NMO-2, and NMO-3.
Class A mobile devices can simultaneously connect to both a GSM and GPRS/EDGE network; i.e., a Class A device supports simultaneous operation of CS and PS connections. In contrast, Class B mobile devices can automatically connect calls from either a GSM or GPRS/EDGE network, but not simultaneously. Once a Class B device has opened a PS connection, incoming CS domain calls are ignored (and vice versa). Lastly, a Class C mobile device must be manually configured to operate in only a GSM, or a GPRS/EDGE network. Class C mobile devices only connect to one network.
Network apparatus are classified into NMOs by paging capabilities and support. Paging has special significance for mixed networks, as will be described in greater detail hereinafter. Briefly, NMO-1 network structures jointly page devices in both the GSM (CS) and GPRS/EDGE (PS) domains. In other words, the network entities (e.g., Mobile Switching Center (MSC), GPRS Support Node (GSN), etc.) maintain internal dialogues to ensure consistent paging of a device in both GSM and GPRS paging channels.
In contrast, NMO-2 only transmits paging messaging in the GSM domain; GPRS services are paged via the existing GSM paging channels. The GSM network entities receive GPRS pages from GPRS network entities; once received, the pages are forwarded via the GSM control channels.
Lastly, NMO-3 configurations completely decouple paging operations between GSM and GPRS networks. Unfortunately, in NMO-3 networks, a mobile device must monitor both GSM and GPRS paging channels simultaneously; as conceivably, a page could be received on either.
Within the context of GSM/GPRS/EDGE paging, subscribers have reported that Class B mobile devices, operating in non-DTM NMO-2 networks, may miss CS voice calls. Furthermore, the problem is significantly exacerbated in Packet Switched data services that have persistence (e.g., static IP applications, such as “push” data notifications, etc.). Unfortunately, recall that NMO-2 network entities only provide paging messages using the existing GSM channels; however, once a Class B mobile device is occupied with GPRS/EDGE service, GSM messaging is ignored. Clearly, the prior art GSM/GPRS/EDGE solutions for combining CS and PS domain operation suffers from a “blind spot” in operation.
Thus, improved solutions are required for paging operation within, e.g., GSM/GPRS/EDGE networks. Such improved solutions should fully support the entire network transition from GSM, through GPRS and EDGE networks without adversely impacting user experience. More generally however, improved methods and apparatus are needed for paging within coexisting networks. Such improved solutions should ideally enable transitions from a first network to a second network under normally exclusionary conditions.